1. Field of the Invention
This invention relates to techniques for cleaning, stimulating, purging and unloading fluids from gas and oil wells and more particularly, to well stimulation and purging compositions for enhancing gas and oil production in gas- and condensate-type wells by dissolving solids such as salt, drilling mud, iron sulfide, iron oxide and other minerals and by retarding and dispersing bacteria by flocculating and foaming the solids, minerals, bacteria and fluids from the well. This cleansing action of the composition enhances production by reducing or eliminating hydrostatic back pressure in the wells. The compositions include two base solutions which can be used either alone or in selected combinations with each other, depending on well conditions, in well cleanup, well stimulation or formation purging applications. The first base solution is an anionic surfactant characterized by an aqueous solution of ether sulfate, isopropanol anhydrous, ammonium bisulfide, and either potassium chloride or a clay stabilizer formulation. In batch treatment of oil wells and gas wells, the solution is capable of flocculating water, condensate, bacteria, solids and minerals in the wells, reducing surface tension of well fluids and retarding, dissipating and dispersing the bacteria and various solids and minerals by foaming these to the well surface. This cleansing action substantially clears the well formation, "rat hole" and well bore and enhances total oil and gas production. The solution can also be used to purge water and condensate from the well formation in order to eliminate or reduce water and condensate coning in the well. The solution can be used for continuous injection down the well casing or short string, capillary string or the like tubing to facilitate a 24-hour water and condensate unloading process from the well, as well as dissolving and unloading solids and minerals and removing bacteria from the well. Other selected water-soluble inhibitors such as corrosion, scale, quaternary quats, surfactants and the like can be added to the diluted solution to address other well problems, according to the knowledge of those skilled in the art. The second base solution is a cationic surfactant which is "ambiguous", or can emulsify both water and hydrocarbons in solution, and is characterized by a homogenous solution of a coco diamine amido benzyl chloride type quaternary compound, isopropanol anhydrous, ammonium bisulfide, and potassium chloride or a clay stabilizer formulation for use in extracting condensate from gas or oil wells. The first and second base solutions are applied either individually or typically, in combination with each other, depending on well conditions, to the gas and oil wells in order to substantially clear water, bacteria, solids and iron, salt and other mineral deposits, as well as oil condensate, from the wells and significantly enhance gas and oil production, respectively, from the wells. Under circumstances in which condensate contributes little or no impediment to production, the first base solution can be used alone. Under circumstances in which condensate is a major impediment to production, the second base solution is used alone or typically, in combination with the first base solution, in which case the second base solution is applied to the well typically at a quantity of about 30% by volume of the quantity of first base solution.
In the oil and gas industry, wells which have been operable for many years in the production of oil and gas frequently decrease in productivity due to a number of factors. One of the most common impediments to well productivity is water coning, which occurs when water, frequently in the form of aqueous brines, flows from the well formation and into the well casing annulus in a process called water coning. When a pressure drop is subsequently applied to the well in order to produce the oil to the well surface, the water is extracted from the well in quantities which exceed that of the oil or gas. Consequently, the water must be drawn from the well and separated from the oil or gas, and this increases the cost of oil or gas production from the well. The presence of water coning in the well further impedes oil or gas production by forming salt and other mineral deposits in the well. While a variety of techniques have been used for removing fluids from the well, the salt and other minerals typically remain in the form of deposits which partially or completely block the well, such that deposits of these minerals remain a problem in the production of oil and gas from the well after removal of the water and condensate.
2. Description of the Prior Art
Various compositions having surfactant, emusifyng or cleansing properties are known in the art. Typical of these compositions is the "Formulated Branched Chain Alcohol Ether Sulfate Compounds" described in U.S. Pat. No. 5,562,866, dated Oct. 8, 1996, dated Oct. 8, 1996, to Patrick C. Hu, et al. The compounds are characterized by double-tailed alcohol ether sulfates of specified chemical structures which are formulated with a hydrotrope or a co-surfactant. The formulations are useful for various surfactant utilities including use in hard water systems. A "Thickened, Highly Aqueous, Cost Effective Liquid Detergent Compositions" is detailed in U.S. Pat. No. 5,587,356, dated Dec. 24, 1996, to Shelley L. Dauderman, et al. The compositions are characterized by low-cost, effective aqueous heavy duty liquid laundry detergent compositions. The compositions contain relatively low levels of an anionic/nonionic-based surfactant system with a protease-containing enzyme component, a low-cost viscosity-enhancing agent and relatively large amounts of water. The anionic component of the surfactant system includes a combination of alkyl sulfate and alkyl ether sulfate. The nonionic component of the surfactant system includes fatty alcohol ethoxylates. U.S. Pat. No. 5,679,877, dated Oct. 21, 1997, to Rita Erilli, et al., discloses a "Thickened Liquid Cleaning Composition Containing an Abrasive". The composition includes a paraffin sulfonate, an ethoxylated alkyl ether sulfate, and optionally, a zwitterionic betaine suriactant, a Laponite day thickener and water. U.S. Pat. No. 5,705,467, dated Jan. 6, 1998, to Clement K. Choy, describes "Thickened Aqueous Cleaning Compositions and Methods of Use", characterized by a thickening agent including an alkyl ether sulfate surfactant which forms about 0.1 to about 10% by weight of the composition, about 0.1-5.0% by weight of a cothickening surfactant including an alkali metal fatty acid sulfate and/or an alkoxylated alkylphenol sulfate salt, a solvent selected from the class consisting of terpene derivatives including a functional group and tertiary alcohols which form about 0.01 to about 10% by weight of the composition, and an electrolyte component in an amount effective for enhancing thickening effects of the alkyl ether sulfate surfactant and solvent. A "High Foaming Nonionic Surfactant Based Liquid Detergent" is disclosed in U.S. Pat. No. 5,707,955, dated Jan. 13, 1998, to Gilbert S. Gomes, et al. The detergent is characterized by a disenfecting agent, four essential surfactants including a water-soluble nonionic surfactant, an ethoxylated alkyl ether sulfate anionic surfactant, two sulfonate surfactants, and water. U.S. Pat. No. 5,728,654, dated Mar. 17, 1998, to James W. Dobson, Jr., et al., discloses "Stabilized Fluids Containing Soluble Zinc", characterized by low solids, high density fluids which are useful as drilling, workover, and completion fluids and the like in oil and gas well operations. The fluids include a brine having dissolved therein a zinc salt such as zinc bromide, and optionally one or more additional water soluble salts, a viscosifier which is a high surface area silica, a biopolymer viscosifier, a fluid loss control additive which is preferably a starch derivative, zinc carbonate, and optionally, an alkaline buffer, a polar additive and a bridging agent. U.S. Pat. No. 5,767,050, dated Jun. 16, 1998, to Steven Adamy, details "Light Duty Liquid Cleansing Compositions Comprising Partially Esterified Polyhydric Alcohol Solubilizing Agent". The compositions include a biodegradable solubilizing agent, a water soluble, foaming, ethoxylated alkyl ether sulfate anionic surfictant, and optionally, a nonionic surfactant and a water soluble, foaming zwitterionic betaine surfactant.
An object of this invention is to provide well stimulation and purging/squeezing compositions for enhancing gas or oil production in gas and condensate type wells.
Another object of this invention is to provide well stimulation and purging compositions which are capable of batch treatment or continuous injection of oil and gas wells to facilitate removal of fluids, bacteria and various solids, salt and other mineral deposits from the wells, or purging of fluids from the well formations in order to reduce or eliminate fluid coning in the wells.
Still another object of this invention is to provide a well stimulation and purging composition characterized by an anionic surfactant which is an aqueous solution of ether sulfate, isopropanol anhydrous, ammonium bisulfide, and potassium chloride or a clay stabilizer formulation, and the solution is capable of batch application to oil and gas wells for the flocculating and foaming of water, condensate, bacteria and dissolved solids, salt and other minerals to the well surface in order to substantially unblock the well, and which solution can be used in the purging of water from the formation outside the well casing in order to eliminate or reduce water coning in the well. The solution can be used to facilitate continuous unloading of water, condensate, bacteria and dissolved solids, iron, salt and other minerals from the well.
Yet another object of this invention is to provide a well stimulating and purging composition characterized by a cationic, soluble surfactant foamer which is "ambiguous", or capable of emulsifying both oil and water, in well fluids, and is characterized by a homogenous solution of a coco diamine amido benzyl chloride type quaternary compound, isopropanol anhydrous, ammonium bisulfide, and potassium chloride or a clay stabilizer formulation, which composition is used primarily for extracting condensate from oil and gas wells.
A still further object of this invention is to provide a method of enhancing oil and gas production by cleaning, stimulating or purging oil and gas wells.